83 lines
3.2 KiB
Nix
83 lines
3.2 KiB
Nix
# | Build a script to install and start a set of systemd units on any
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# systemd-based system.
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#
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# Creates a symlink at /etc/systemd-static/${namespace} for slightly
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# improved atomicity.
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{ writeScriptBin
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, bash
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, coreutils
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, systemd
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, runCommand
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, lib
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}:
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{ units # : AttrSet String (Either Path { path : Path, wanted-by : [ String ] })
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# ^ A set whose names are unit names and values are
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# either paths to the corresponding unit files or a set
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# containing the path and the list of units this unit
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# should be wanted-by (none by default).
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#
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# The names should include the unit suffix
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# (e.g. ".service")
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, namespace # : String
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# The namespace for the unit files, to allow for
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# multiple independent unit sets managed by
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# `setupSystemdUnits`.
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}:
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let static = runCommand "systemd-static" {}
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''
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mkdir -p $out
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${lib.concatStringsSep "\n" (lib.mapAttrsToList (nm: file:
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"ln -sv ${file.path or file} $out/${nm}"
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) units)}
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'';
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add-unit-snippet = name: file:
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''
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oldUnit=$(readlink -f "$unitDir/${name}" || echo "$unitDir/${name}")
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if [ -f "$oldUnit" -a "$oldUnit" != "${file.path or file}" ]; then
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unitsToStop+=("${name}")
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fi
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ln -sf "/etc/systemd-static/${namespace}/${name}" \
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"$unitDir/.${name}.tmp"
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mv -T "$unitDir/.${name}.tmp" "$unitDir/${name}"
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${lib.concatStringsSep "\n" (map (unit:
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''
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mkdir -p "$unitDir/${unit}.wants"
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ln -sf "../${name}" \
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"$unitDir/${unit}.wants/.${name}.tmp"
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mv -T "$unitDir/${unit}.wants/.${name}.tmp" \
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"$unitDir/${unit}.wants/${name}"
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''
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) file.wanted-by or [])}
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unitsToStart+=("${name}")
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'';
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in
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writeScriptBin "setup-systemd-units"
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''
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#!${bash}/bin/bash -e
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export PATH=${coreutils}/bin:${systemd}/bin
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unitDir=/etc/systemd/system
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if [ ! -w "$unitDir" ]; then
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unitDir=/etc/systemd-mutable/system
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mkdir -p "$unitDir"
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fi
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declare -a unitsToStop unitsToStart
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oldStatic=$(readlink -f /etc/systemd-static/${namespace} || true)
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if [ "$oldStatic" != "${static}" ]; then
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${lib.concatStringsSep "\n"
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(lib.mapAttrsToList add-unit-snippet units)}
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if [ ''${#unitsToStop[@]} -ne 0 ]; then
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echo "Stopping unit(s) ''${unitsToStop[@]}" >&2
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systemctl stop "''${unitsToStop[@]}"
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fi
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mkdir -p /etc/systemd-static
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ln -sfT ${static} /etc/systemd-static/.${namespace}.tmp
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mv -T /etc/systemd-static/.${namespace}.tmp /etc/systemd-static/${namespace}
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systemctl daemon-reload
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echo "Starting unit(s) ''${unitsToStart[@]}" >&2
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systemctl start "''${unitsToStart[@]}"
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else
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echo "Units unchanged, doing nothing" >&2
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fi
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''
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